Precompilers, OCI & OCCI :: PLS-00306 / Wrong Number Or Types Of Arguments In Call To Existing Stored Procedure

I'm using an existing stored procedure in my C code. The stored procedure in question has been compiled and is proven to work without any errors. However, when I use the same in my C code, its failing with the above error.

The Store procedure definition looks like :

CREATE OR REPLACE FUNCTION SP(
srq_id integer ,
unid IN SPkg.arr_parmid,
parm_typ IN SPkg.arr_parm_typ,

[code].....

Type definitions

TYPE arr_parm_typ IS TABLE OF char INDEX BY BINARY_INTEGER;
TYPE arr_parmid IS TABLE OF tbl_parm.UNID%TYPE INDEX BY BINARY_INTEGER;
TYPE arr_parm_lbl IS TABLE OF tbl_parm.PARM_LBL%TYPE INDEX BY BINARY_INTEGER;
TYPE arr_parm_vlu IS TABLE OF tbl_parm.PARM_VLU%TYPE INDEX BY BINARY_INTEGER;
TYPE arr_vlu_hint IS TABLE OF tbl_parm.VLU_HINT%TYPE INDEX BY BINARY_INTEGER;

My C code looks like :

typedef struct param
{
char lbl[30][81];
char vlu[30][256];
char typ[30];
ub8 seq_no[30];

[code].....

The way I invoke the stored procedure:

char command[250] = "begin
:retval := SSP_srq_parm_all(:srq_id,:unid,:parm_typ,:parm_lbl,:parm_vlu,:commit_flag,:vlu_hint,:create_flag);
end;";
OCIStmtPrepare2((OCISvcCtx *)svchp, (OCIStmt **)&(stmthp),
(OCIError *)errhp, (OraText *)command,

[code].....

OCIStmtExecute() fails with the above error.